Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-05-04
Astronomy and Astrophysics
Astrophysics
7 pages, 5 figures, 4 tables. Accepted for publication in A&A, on April 27 2006
Scientific paper
10.1051/0004-6361:20064960
In this paper we present a new, accurate determination of the three components of the absolute space velocity of the Galactic globular cluster NGC6397 (l 338d, b -12d). We used three HST/WFPC2 fields with multi-epoch observations to obtain astrometric measurements of objects in three different fields in this cluster. The identification of 33 background galaxies with sharp nuclei allowed us to determine an absolute reference point and measure the absolute proper motion of the cluster. The third component has been obtained from radial velocities measured on spectra from the multi-fiber spectrograph FLAMES at UT2-VLT. We find [mu_alpha cos(delta), mu_delta](J2000.0) = [+3.39 +/- 0.15, -17.55 +/- 0.15] mas/yr, and V_rad = +18.36 +/- 0.09 (+/-0.10) km/s. Assuming a Galactic potential, we calculate the cluster orbit for various assumed distances, and briefly discuss the implications.
Anderson Jeffrey
Bedin Luigi R.
Carraro Giovanni
King Ivan R.
Milone André
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